Antarctic Peninsula Climate Variability: Observations, Models, and

Antarctic Peninsula
Climate Variability:
Observations, Models, and Plans for IPY Research
May 14-16, 2006
University of Colorado • Boulder, CO, USA
http://nsidc.org/events/IPY_APCV/
Antarctic Peninsula Climate Variability:
Observations, Models, and Plans for IPY Research
Hosted by the National Snow and Ice Data Center at the University of Colorado
Table of Contents
Introduction ............................................................................... 3
Agenda ....................................................................................... 6
Abstracts.................................................................................... 9
Oral Presentations ................................................................................. 9
Poster Presentations ........................................................................... 22
Participants.............................................................................. 31
Notes ........................................................................................ 36
Organizing Committee at NSIDC/CIRES,
University of Colorado
Ted Scambos
Cindy Brekke
Betsy Sheffield
Lindsay Husted
Kara Pharris
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Introduction
Recent events in the Antarctic Peninsula (AP) demonstrate that ice and climate
systems can change rapidly in a warming world. Air temperatures in the AP have
risen six times faster than the global average in recent decades, which has triggered
glaciological and ecological events in the last 1,000 years that are unique in the
history of the region. Studies based on remote sensing and the available in situ data
show that a complex interaction is underway, one that involves climate warming,
air and ocean circulation changes, sea ice retreat, and surface and basal melting of
land and shelf ice. Such changes have contributed to melt percolation and
fracturing, seasonal fluctuations in ice flow, and rapid glacial acceleration in the
aftermath of shelf breakup. As shelves disintegrate, they uncover a glacial history
preserved on the seafloor beneath them, indicating that the current retreats are rare
to unprecedented in the Holocene. Biological and oceanographic studies are active
along both coasts, as scientists strive to understand how ocean currents and
ecosystems migrate during climate change. During a period of rapid change, the
recent discovery of a new chemotrophic ecosystem native to the sub-iceshelf
environment confirms that there are still unknowns in the Earth and life systems
of the AP.
The goals of the Antarctic Peninsula Climate Variability (APCV) workshop are:
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Present the most recent research results and identify the current frontiers
of knowledge in the AP ice and climate systems.
Discuss evolving research plans for the IPY period, and promote the
formation of collaborative interdisciplinary research groups.
Provide a forum for graduate-student presentations.
Discuss outreach ideas and plans for IPY-AP activities.
Discuss national and international logistical assets and possible logistical
linkages for conducting IPY-period field work.
The workshop reviews recent high-profile research results. Warming has continued
in the AP area through at least 2003 (Skvarca and DeAngelis, 2003; Morris and
Vaughan, 2003), and an exceptional weather pattern in 2002 led to both
unprecedented summer warming and intense, prolonged surface melting, which
culminated in the disintegration of the Larsen B ice shelf (van den Broeke, 2005;
Rack and Rott, 2005, in press; Scambos et al., 2003). Subsequent to this
disintegration, significant glacier acceleration and thinning occurred (Rignot et al.,
2004; Scambos et al., 2004), confirming the link between ice shelf stability and
glacier force balance. This had been previously suggested by observations of the
Larsen A feeder glaciers and the valley walls of the Larsen B glaciers (Rack and
Rott, 2002; DeAngelis and Skvarca, 2003). More broadly, a survey of aerial and
satellite photos spanning 50+ years has shown that glaciers throughout the region
north of 70° S are presently in retreat, and that this retreat progressed southward
as climate warmed in the region in previous decades (Cook et al., 2005). There is
substantial evidence emerging that many AP glaciers undergo seasonal
accelerations due to meltwater percolation, which hastens the mass balance
changes in the ice sheet as the melt season lengthens.
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Sea ice and ocean circulation changes in the region are also profound and are likely
a part of the amplified warming this region has seen. Comiso (2000) and Parkinson
(2002) have described a trend of 20% sea ice decline in the past few decades in the
Bellingshausen Sea. Ocean circulation may be changing on the western AP
continental shelf (Martinson, 2005) and there is a possibility of changes
propagating from the AP in the form of increasing or decreasing rates of bottom
water formation as new sites of dense water production are created by ice shelf and
glacier changes (Gordon et al., 2001).
Causes of the warming are uncertain, but several model-based theories are
emerging with robust support from observation. Thompson and Solomon (2002)
show that a large fraction of the warming is likely due to stratospheric cooling, a
result of autumn ozone depletion. Liu et al. (2003) and many others suggest that
changes in the frequency and intensity of the Antarctic Oscillation and the
Southern Oscillation explain part of the warming signal. Raphael (2003) shows that
the third-order wave in the circumpolar tropospheric circulation changed
significantly around 1975, and the pattern now tends to force warmer,
northwesterly flow across the peninsula.
Results from marine geological work are also stunning. Earlier work on the
exposed Larsen A seabed, and in the Prince Gustav Channel to the north, revealed
that these areas had seen previous retreats of their ice shelf covering, coinciding
with warmer global climate episodes in the recent past (such as the Medieval Warm
Period, and the period between 2500 and 3500 BCE; Pudsey et al., 2001;
Brachfield et al., 2003). But, the retreat of the Larsen B in 2002 is apparently
unprecedented in this interglacial epoch (Domack et al., 2005).
The Antarctic Peninsula may well be a model for a future, warmer Antarctica.
What we see there are changes of greater scale, speed, and magnitude than were
considered possible before. This meeting will be a step towards understanding this
system and its responses, knowing what the future may hold, and planning future
field observations and research.
This is the third in a series of workshops focused on the topic of Antarctic
Peninsula Climate Variability (APCV), following workshops at Hamilton College,
New York, USA (April 2002) and University of Cambridge, Cambridge, England
(September 2004).
Funding support for the “Antarctic Peninsula Climate Variability: Observations,
Models, and Plans for IPY Research” workshop is provided by the National
Science Foundation grant OPP-0550099, CIRES, and the National Snow and Ice
Data Center.
References
Cook, A., A. Fox, D. Vaughan, and J. Ferrigno. 2005. Retreating glacier fronts on the
Antarctic Peninsula over the past half-century. Science 308, 541-544.
Comiso, J. 2000. Variability and trends in Antarctic surface temperatures from in situ and
satellite infrared measurements. Journal of Climate 13, 1674-1696.
De Angelis, H, and P. Skvarca. 2003. Glacier surge after ice shelf collapse. Science 299
(5612), 1560-1562.
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Domack, E., D. Duran, A. Leventer, S. Ishman, S. Doanne, S. McCallum, D. Ambias, J.
Ring, R. Gilbert, and M. Prentice. 2005. Stability of the Larsen B ice shelf on the Antarctic
Peninsula during the Holocene epoch. Nature 436(4), 681-685.
Domack, E., S. Ishman, A. Leventer, S. Sylva, V. Wilmont, and B. Huber. 2005. A
chemotrophic ecosystem found beneath Antarctic ice shelf. Eos 86(29), 269-272.
Gordon, A. .L., M. Visbeck, and B. Huber. 2001. Export of Weddell Sea Deep and Bottom
Water. Journal Geophysical Research 106(C5), pp. 9005-9017.
Liu, J., J. Curry, and D. Martinson. 2004. Interpretation of recent Antarctic sea ice
variability. Geophysical Research Letters 31, doi:10.1029/2003GL018732.
Martinson, D. 2005. Distribution and ventilation of ocean heat on the western Antarctic
Peninsula continental shelf. Geophysical Research Abstracts 7, 10293, SRef-ID: 16077962/gra/EGU05-A-10293.
Morris, E., and D. Vaughan. 2003. Spatial and temporal variation of surface temperature
on the Antarctic Peninsula. In Antarctic Peninsula Climate Variability: Historical and
Paleoenvironmental Perspectives. Ed. E. Domack et al. Special Issue, Antarctic Research
Series 79, 61-68.
Parkinson, C. 2002. Trends in the length of the southern ocean sea ice season, 1979-99.
Annals of Glaciology 34, 435-440.
Raphael, M., 2003. Impact of observed sea ice concentration on the Southern Hemisphere
extratropical atmospheric circulation in summer. Journal of Geophysical Research 108 (D22),
doi:10.1029/2002JD03308.
Rack. W., and H. Rott. In press. Pattern of retreat and disintegration of Larsen B ice shelf,
Antarctic Peninsula. Annals of Glaciology 39.
Rignot, E., G. Casassa, P. Gogineni, W. Krabill, A. Rivera, and R. Thomas. 2004.
Accelerated ice discharge from the Antarctic Peninsula following the collapse of Larsen B
ice shelf. Geophysical Research Letters 31, L18401, doi:10.1029/2004GL020697.
Rott, H., W. Rack, R. Skvarca, and H. De Angelis. 2002. Northern Larsen Ice Shelf,
Antarctica: further retreat after collapse. Annals of Glaciology 34, 277-282.
Scambos, T., C. Hulbe, and M. Fahnestock. 2003. Climate-induced ice shelf disintegration
in the Antarctic Peninsula. In Antarctic Peninsula Climate Variability: Historical and
Paleoenvironmental Perspectives. Ed. E. Domack et al. Special Issue, Antarctic Research
Series 79, 77-92.
Scambos, T. J. Bohlander, C. Shuman, and P. Skvarca. 2004. Glacier acceleration and
thinning after ice shelf collapse in the Larsen B embayment, Antarctica. Geophysical Research
Letters 31, L18402, doi:10.1029/2004GL020670.
Skvarca, P. and H. De Angelis. 2003. Impact assessment of regional warming on glaciers
and ice shelves of the northeastern Antarctic Peninsula. In Antarctic Peninsula Climate
Variability: Historical and Paleoenvironmental Perspectives. Ed. E. Domack et al. Special
Issue, Antarctic Research Series 79, 69-78.
Van den Broeke, M. 2005. Strong surface melting preceded collapse of Antarctic Peninsula
ice shelf. Geophysical Research Letters 32, L12815, doi:10.1029/2005GL023247.
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Agenda
Sunday May 14
NSIDC meeting rooms at 1540 30th Street, Boulder, Room 151
5:00 pm – 7:00 pm Pre-Meeting Registration, Poster Show for NSIDC Posters,
and Reception
Monday May 15
APCV-III Meeting at Folsom Stadium Conference Center (5th floor,
East Side Folsom Stadium)
Morning Continental breakfast at Millennium Harvest House Hotel
8:00 am
Registration begins
Poster set up
8:30 am
Introductions, agenda, and workshop information – Ted Scambos
8:50 am
Welcome from NSIDC Director – Roger Barry
Welcome from CIRES Associate Director – Bill Lewis
9:10 am
IPY Outlook – Mark Parsons, NSIDC
9:30 am
Keynote Speaker: "A century of climate change in the Antarctic
Peninsula" by Dr. Susan Solomon
10:10 am
Break
10:25 am
1st Session: Climate and Oceans, Past and Present, in the AP
Invited Speakers (20-minute presentations, 5 minutes for questions)
Contributed talks (15-minute presentations, 5 minutes for questions)
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12:15 pm
Lunch: Colorado Deli sandwich buffet
1:05 pm
2nd Session: Climate and Oceans, Past and Present, in the AP
Invited Speakers (20-minute presentations, 5 minutes for questions)
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2:20 pm
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Dr. Marilyn Raphael (Invited)
Dr. Douglas Martinson (Invited)
Dr. Michael Meredith (Contributed)
Dr. Gareth Marshall (Contributed)
Dr. Alberto Setzer (Contributed)
Break
Dr. Jefferson Simões
Dr. David Vaughan
Dr. Robert Massom
2:35 pm
3rd Session: Ice Shelves/Glaciers in a Warming Climate
Invited Speakers (20-minute presentations, 5 minutes for questions):
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Dr. Wolfgang Rack
Dr. Ian Joughin
Dr. Andrew Shepherd
3:50 pm
Break
4:05 pm
4th Session: Ice Shelves/Glaciers in a Warming Climate (continued)
Contributed talks (15-minute presentations, 5 minutes for questions):
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Ms. Daniella Jansen
Dr. Christopher Shuman
Dr. Olga Sergienko
Dr. Ted Scambos
5:25 pm
Poster Session: One minute introduction to posters
5:40 pm
Browse posters (posters will be displayed for entire meeting)
Cash bar available
7:30 pm
Meeting Dinner at Millennium Harvest House
Tuesday May 16
APCV-III Meeting at Folsom Stadium Conference Center (5th floor,
East Side Folsom Stadium)
Morning Continental breakfast at Millennium Harvest House Hotel
8:30 am
Registration
8:40 am
Keynote Speaker: “Glaciological Evidence for Abrupt Climate
Change: Past and Present” by Dr. Lonnie Thompson
9:20 am
5th Session: Climate and Oceans, Past and Present, in the AP
(continued)
Contributed talks (15-minute presentations, 5 minutes for questions):
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Dr. David Schneider
Mr. Carlos Moffat
Dr. Sharon Stammerjohn
10:20 am
Break
10:40 am
6th Session: Marine Geology/Biology
Invited Speakers (20-minute presentations, 5 minutes for questions)
Contributed talks (15-minute presentations, 5 minutes for questions)
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Dr. Bill Fraser (Invited)
Dr. Amy Leventer (Invited)
Dr. Eugene Domack (Invited)
Ms. Michèle Koppes (Contributed)
Ms. Kristy Milliken (Contributed)
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12:35 pm
Lunch: Arriba! Mexican buffet
1:35 pm
IPY-AP Overview (format TBD)
Science Plan, Logistics, Outreach:
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Dr. Jefferson Simões
Dr. Ted Scambos
Mr. Mark Parsons
Dr. David Vaughan
Dr. Eugene Domack
Mr. Mark McCaffrey
3:00 pm
Break
3:15 pm
Discussion Groups on IPY-AP plans
5:00 pm
Adjourn workshop
Abstracts
Oral Presentations
Environmental change across the Northern Antarctic Peninsula,
evaluating the reach of global processes
Eugene Domack (Invited Speaker)
The fundamental changes taking place across the Northern Antarctic Peninsula
present the scientific community with the rare opportunity to evaluate regionalscale processes as they may be impacted by, and/or impact, global scale
perturbations in our environment. Only by collecting a set of interlinked and
complimentary data sets from the marine, cryospheric, atmospheric, and biotic
systems will we be able to move forward in understanding earth systems in this
rapidly changing polar region. The collapse of the Larsen A and B shelves in recent
years has not only demonstrated strong feedback relationships to oceanographic
circulation and terrestrial glaciers but has also revealed an unprecedented view of
the seascape beneath a long-lived ice shelf setting from the near coastal grounding
lines to the distal calving fronts, which have been historically documented for over
150 years.
The new seafloor contains the first documented existence of a chemotrophic
ecosystem beneath an ice shelf setting, and the first such ecosystem for the entire
Antarctic plate. The new influx of seasonal phytoplankton detritus upon the
seafloor represents a modern case example of permissive ecology, a concept widely
used (but rarely observed) to describe environmental perturbations and
evolutionary jumps following the aftermath of large scale mass extinctions and/or
extreme habitat change. The role of glaciation and bedrock geology in the
development of the chemotrophic habitat is as yet unclear, but this example
provides us with the possibility that life in extreme environments may indeed be
stimulated by glaciation, rather than simply exist in spite of it. The morphology of
the seafloor also provides a vital link in understanding how and why terrestrial
glaciers have surged, following the ice shelf collapse. Deep troughs (well over 1200
m) exist within and near the former grounding lines of the ice shelf and these are
now converting to fjords, as valley glaciers retreat, in-step with increased flow
velocity, during and after the surge. Hence, the dynamic link between ice shelf and
contributory glaciers is more complex than a simple buffer effect, of the former
upon the later. The time scale of change and climate induced nature of ice shelf
collapse also needs to be placed into a paleoclimate perspective. While excellent
marine sediment cores exist for parts of the area, we urgently need confirmation of
our marine proxy data from independent time series, archives that only ice cores
can provide; at present none exist for the region. These important records could
be obtained from across a linear plateau (2 km in elevation) and would be ideally
located to intercept changing records of meridonal and zonal circulation across the
northern AP. The dominance of the later (during strong southern annular modes
in circulation) are thought to be tied to decreases in stratospheric ozone, and hence
may not be a particularly strong feature of paleoclimate during the Holocene when
anthropogenic influence upon ozone loss were not occurring. Deep ventilation of
the Weddell Sea is also tied to circulation beneath the ice shelves and there are
signs that this process as well as mid-depth water masses are in a state of flux.
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The unique and catastrophic decay of the regions ice shelves under regional
warming demands serious investigation into all of these questions and provides, by
the vacancy of ice cover, a unique opportunity to examine earth system linkages at
an epic level during the IPY.
Western Antarctic Peninsula glacial history and its importance to
understanding contemporary marine ecosystem structure and
function
William R. Fraser, Hugh W. Ducklow (Invited Speaker)
As fields of study, ecology and glaciology have historically remained intellectually
isolated from one another. A major barrier limiting the exchange of information
between these two disciplines is due to the inherent differences that exist in the
temporal scales that define discipline-specific processes of interest. As a result,
both ecologists and glaciologists tend to operate with little appreciation of how
decadal to millennial-scale processes interact to shape the structure and function of
contemporary ecosystems. The Western Antarctic Peninsula marine ecosystem
exhibits extreme heterogeneity in the distribution of a number of biological
populations and properties. Research during the last 15 years in particular by the
Palmer Long Term Ecological Research Program has shown that this
heterogeneity can be attributed directly to the effects of past glacial events on
regional bathymetry. One of the most conspicuous examples of this heterogeneity
is the distribution of Adélie penguins, whose breeding populations occupy only
five locations along the entire length of the WAP. These locations are associated
with deep, glacially-incised canyons that reach from the land margin to the shelf
break. These canyons function as conduits for Circumpolar Deep Water that
upwells near the land margins, altering heat and nutrient budgets, and ultimately
encouraging the growth of phytoplankton communities favorable to the krill and
fish on which Adélie penguins depend. These conditions satisfy a most critical
component of the life history of Adélie penguins, which as flightless predators
require access to nearby, ecologically predictable sources of prey to breed
successfully and survive winter. These dynamics establish an intellectual and
empirical bridge between disciplines that may lead to more robust models of WAP
ecosystem processes and their response to continued climate warming.
Basal melting of tabular icebergs: a mixed layer approach
D. Jansen, M. P. Schodlok, W. Rack, H. Sandhaeger
Drifting tabular icebergs represent large natural ice bodies under influence of
rapidly changing boundary conditions. To study the change of iceberg geometry
during its drift an iceberg evolution model was applied to several icebergs from the
Weddell Sea region. Basal erosion dominates these changes, releasing a
considerably large amount of cool melt water into the Southern Ocean.
Comparison with ICESat GLAS data, however, showed that melt rates in lower
latitudes are only half of melt rates predicted with a simple thermohaline ice-shelfocean-interaction model. Model experiments with a new melting approach, i.e. the
melt rate was fitted by varying the turbulent exchange parameter for temperature
(gammaT) and salt (gammaS), identified two melting regimes: (1) In the Weddell
Sea gammaT is set to 0.001 m/s due to the slow drift velocity of about 5 km/day
and several grounding phases. (2) In the Scotia Sea T is set to 5*10-5 m/s, as the
iceberg drifts unhindered with the ocean current (about 15 km/day) and is
surrounded by more melt water, having a larger cooling effect. gammaS is set to
0.00505 gammaT in both cases.
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In order to improve the solution with respect to the melt water plume we followed
a mixed layer approach for the ice-ocean boundary. We will present first results
from this mixed layer iceberg melting approach.
A recently funded analysis of rapidly changing Antarctic ice shelves
using ERS and GLAS altimetry, RADARSAT SAR interferometry and
3-D ocean modeling
I. Joughin, L. Padman, and H. Fricker (Invited Speaker)
We are beginning a detailed analysis of Antarctic ice shelves that have undergone
recent rapid change, focusing on the role of ocean-ice interactions in thinning the
Larsen B, Larsen C, and Pine Island Bay (PIB) ice shelves. Our long-term goal is to
contribute towards an answer to the question: In a changing climate, what role do
Antarctica’s ice shelves play in controlling the mass balance of the Antarctic ice
sheet, and thus Antarctica’s contribution to global mean sea level? Because this
project has begun, we will focus on similar results from other ice shelves.
Sediment yields and associated glacier dynamics from Patagonia to
the Antarctic Peninsula
Michèle Koppes, Bernard Hallet, John Anderson
We will present results from a multi-year study of ice dynamics and sediment
fluxes along a transect of tidewater glaciers from Patagonia to Antarctica. Using
seismic profiling and piston coring near the terminus, we measured the decadal
and centennial sediment yields from three glaciers in Patagonia. These yields are
compared to modeled ice fluxes from NCEP reanalysis data, to understand the
relationship between ice dynamics and glacial erosion rates. We will be continuing
the transect with a cruise on the Palmer to the Antarctic Peninsula during IPY to
collect seismic data and cores in the fjords, and to measure ice thickness and
velocities on the adjacent glaciers. We also seek collaboration in setting up longerterm climate stations around the Peninsula as part of our field effort.
Diatom assemblages from the ex-Larsen A and B ice shelf regions: a
comparison of the modern and Holocene record
Amy Leventer, Nicky West, Maureen Lynch, Eugene Domack (Invited
Speaker)
The breakup of the Larsen A and B ice shelves, in 1995 and 2002 respectively, has
provided a unique opportunity to track the role of pelagic processes in influencing
biogenic sedimentation. Consequently, diatom assemblages in surface water
samples and surface sediments from the ex-Larsen A and B Ice Shelf regions were
analyzed to assess differences between these two regions given the longer time
period that the Larsen A region has been ice shelf free. Downcore analyses were
aimed at investigating the use of diatoms as paleoenvironmental indicators of
changes in glacial and sea ice extent during the Holocene. Water and surface
sediment samples from the ex-Larsen A Ice Shelf region were dominated by
diatoms of the genus Chaetoceros, indicating more productive waters. In contrast,
the genus Fragilariopsis, here comprised mainly of sea ice associated species, was
most abundant in water samples and surface sediments from the ex-Larsen B
region. The strong similarities between the water column diatom assemblages and
those found at the sea floor, and the distinct differences between the two
geographic regions demonstrates that the composition of overlying phytoplankton
blooms is faithfully recorded at the sea floor.
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Limited lateral transport and rapid downward flux of diatoms is indicated further
by the presence of green chloroplasts in the patchy diatomaceous fluff observed at
the sea floor. The dramatic increase in diatom abundance in the upper 5 cm of
each core from the ex-Larsen B region marks the initiation of primary productivity
following the in the 2002 collapse of the ice shelf. A single sub-surface diatom
abundance peak in a core just south of the Seal Nunataks, which separates the
Larsen A and Larsen B regions, is thought to reflect material transported south
during a previous breakout of the Larsen A ice shelf.
The role of a changing summer Southern Annular Mode (SAM) in
warming the Larsen Ice Shelf region
Gareth J. Marshall, Andrew Orr, Nicole van Lipzig, John C. King
Rapid regional summer warming on the east coast of the northern Peninsula has
contributed significantly to the northern Larsen Ice Shelf collapse. A
contemporaneous trend in the summer SAM has resulted in stronger westerlies
across the northern Peninsula, reducing its blocking effect and allowing greater
eastward advection of air masses over it. Subsequent formation of a warm foehn
wind on the lee side and a negative climatological temperature gradient across the
barrier results in a summer surface temperature sensitivity to the SAM three times
greater on the eastern Peninsula than on the west.
12-Years of PAL-LTER: physical oceanography, spatio-temporal
variability and ventilation of ocean heat along the Western Antarctic
Peninsula
Douglas G. Martinson, S. E. Stammerjohn, R. A. Iannuzzi, R. C. Smith
(Invited Speaker)
This presentation focuses on 12 years of physical oceanography data, collected
during the Palmer, Antarctica, Long-Term Ecological Research program (PALLTER) over the continental margin of the western Antarctic Peninsula (WAP).
The physical characteristics, water column structure and spatio-temporal variability
of the various properties, are examined for physically consistent and ecologicallyimportant patterns and modes of variability. Specific findings of note include: (1)
the water masses in the grid are well separated according to bathymetrically
controlled features, dividing the sample domain into 3 sub-regions: slope, shelf and
coastal waters; (2) the Antarctic Circumpolar Current (ACC) is always present
along the shelf-break where Upper Circumpolar Deep Water (UCDW) shows its
farthest southern extent and forms the Southern ACC Front (SACCF); (3)
flooding of UCDW onto the continental shelf provides the heat responsible for
providing approximately 28 Wm-2 on annual average to the WAP, which is
presently undergoing the most recent rapid winter regional warming on Earth. The
spatiotemporal variability of the delivery and distribution of ocean heat is dictated
by the dynamics which are consistent with changes in the state of ENSO (La Niña
drives enhanced upwelling in this region) and in the strength of the Southern
Annular Mode (SAM). The large 1997-1998 El Niño, followed by the transition to
the strong La Niña of 1998-1999 (amplified by a large +SAM) introduced a regime
shift on the shelf, resulting in a jump in ocean heat flux of approximately 3 Wm-2
followed by a linear trend of an equal increase in heat flux each year thereafter.
2002 was an anomalous year coinciding with an extraordinary storm forcing
driving a 10σ increase in the heat content on the shelf (which is shown to be
proportional to the heat flux). These jumps coincide with considerable changes in
sea ice distribution as well.
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Pure UCDW is primarily restricted to the deep canyons on the shelf, with
occasional appearances on the regular shelf floor near the middle of the grid
(presumably an area with enhanced nutrients closer to the surface). Anomalies in
summer sea surface temperatures reflect wind strength (stronger winds mixing
more cold winter water to the surface, with cooler SST; light winds, the opposite).
Extreme sea ice conditions in the Antarctic Peninsula region, their
impact and possible links with the disintegration of the Larsen B Ice
Shelf
Robert Massom, Sharon Stammerjohn, Ted Scambos, John Turner,
Ian Simmonds, et al. (Invited Speaker)
Recent studies have revealed that complex interactions are occurring in the
Antarctic Peninsula (AP). Here, we present case studies of extreme sea ice
conditions resulting from large-scale and persistent anomalies in atmospheric
circulation. The impacts are profound, and indeed paradoxical, with seemingly
counteractive processes occurring simultaneously. Such anomalies deliver aboveaverage snowfall, and cause both extensive ice melt and dynamic thickening – the
latter by compaction against the West Antarctic Peninsula. In 2001/2, this resulted
in the Bellingshausen Sea in an unusually early and rapid (short) retreat season
(negative ice-extent anomaly) driven by ice dynamics. Major ice convergence,
deformation and thickening in turn lead to the atypical persistence of highlycompact coastal ice through summer. Ecological effects were both positive and
negative, the latter including an impact on the growth rate of larval Antarctic krill
and the largest recorded between-season breeding population decrease and lowest
reproductive success in a 30-year Adélie penguin demographic time series.
Evidence is also presented of possible causal links between the 2002 disintegration
of the Larsen B Ice Shelf and anomalous patterns of atmospheric circulation and
associated sea ice distribution in the AP region.
Rapid climate change in the ocean adjacent to the WAP during the
second half of the 20th
Michael P. Meredith, John C. King
The climate of the Western Antarctic Peninsula (WAP) is the most rapidly
changing in the southern hemisphere, with a rise in atmospheric temperature of
nearly 3 °C since 1951 and associated cryospheric impacts. We demonstrate here,
for the first time, that the adjacent ocean showed profound coincident changes,
with surface summer temperatures rising more than 1 °C and a strong upper-layer
salinification. Initially driven by atmospheric warming and reduced rates of sea ice
production, these changes constitute positive feedbacks that will contribute
significantly to the continued climate change. Marine species in this region have
extreme sensitivities to their environment, with population and species removal
predicted in response to very small increases in ocean temperature. The WAP
region is an important breeding and nursery ground for Antarctic krill, a key
species in the Southern Ocean food web with a known dependence on the physical
environment. The changes observed thus have significant ecological implications.
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Deriving a high-resolution-continuous record of climate change for
the past 15,000 cal BP, Maxwell Bay sediment core, South Shetland
Islands
K. T. Milliken, J. B. Anderson, J. S. Wellner, P. Manley, S. Bohaty, B.
Michalchuk
In the Antarctic Peninusla area, a climatic gradient, created by orographic and
oceanographic effects, is manifested in extreme temperature and precipitation
patterns. Thus, the area provides a natural laboratory to study the nature and
timing of climate change at high southern latitudes during the past several
thousand years. Two benchmark long term continuous records can now be
compared; Maxwell Bay, situated in a warm wet subpolar climate setting and
Palmer Deep, located in a cold wet subpolar climatic regime. Both of these records
span the past 14000 years, document the timing of ice pullback from the last glacial
maximum, and provide the means to contrast climate fluctuations in two different
area.
This paper presents the preliminary results from a 108 m sediment core (93%
recovery) recovered from Maxwell Bay (South Shetland Islands). The pre-existing
Palmer Deep cores sampled 50 m of structureless diatom ooze/mud, rhythmically
interbedded diatom ooze and pebbly mud and muddy diatomicton (Domack et. al.,
2001). The alternation of diatom ooze and diatomaceous mud is interpreted to
represent climate driven oscillations of biogenic productivity. Magnetic
susceptibility and other paleoenvironmental proxies track biogenic productivity
and provide a means to quantify decadal, century, and millennia scales of climate
change. Additionally, five global climate intervals are noted including, deglaciation,
climatic reversal, Hypsithermal (Holocene Climatic Optimum), Neoglacial, and
Little Ice Age.
Several radiocarbon dates are used to establish an age model and show significant
variations in sedimentation rates through time. The sedimentation rate variations
correspond to sediment facies changes within the core. High sedimentation rates
(10 to 30 mm/yr) correspond to silty diatomaceous mud with abundant sand
laminae interpreted as proximal glaciomarine facies. Lower sedimentation rates (4
mm/yr) are associated with diatomaceous mud with few sand laminae and
abundant bioturbation, interpreted to represent distal glaciomarine sedimentation.
Preliminary analysis of magnetic susceptibility data shows decadal, century, and
millennial scale cyclicity. Additionally, the character of the magnetic susceptibility
signal changes within the core. The changes correspond to climate intervals noted
in the Palmer Deep cores. Whereas the Palmer Deep record is derived from a
biogenic productivity signal as a proxy for climate; the Maxwell Bay system
potentially records a terrestrial sediment derived signal and is more directly linked
to climatically driven glacial advance and retreat.
A first description of the Antarctic Peninsula Coastal Current (APCC)
Carlos Moffat, Robert Beardsley, Breck Owens
The Southern Ocean Global Ecosystem Dynamics (SO GLOBEC) program aims
to understand the circulation patterns and dynamics of the shelf waters west of the
Antarctic Peninsula (wAP). This region is characterized by a strong seasonal cycle
of surface forcing, with a fully ice-covered shelf during the winter which melts
almost completely during the spring. The mountainous land mass of the Peninsula
also provides a source of fresh water during the warmer ice-free season.
14
The SO GLOBEC data set, including drifter trajectories, a year long mooring
record as well as density and underway velocity profiles from large scale
hydrographic cruises, reveals the presence of a large (approximately 30 km wide,
150 m deep) coastal buoyant current attached to the coast of the Peninsula. The
Antarctic Peninsula Coastal Current (APCC) flows south along the coast during
the ice-free season and disappears during the winter, shortly after the onset of ice
on the shelf. Although coastal buoyant plumes are typically associated with river
discharge in mid-latitudes, fresh water from melting glaciers provides a line
buoyancy source for the formation of the APCC. This work provides a first
description of the AICC, a discussion of the mechanisms involved in its formation
and evolution (including fresh water fluxes and down welling - favorable wind
forcing) and its role in the advection of biologically relevant tracers.
Satellite observations of ice acceleration and numerical studies of
the flow regime at Larsen Ice Shelf
W. Rack, H. Rott, D. Jansen, H. Sandhaeger, C. Riedl (Invited
Speaker)
We studied the dynamic behavior of Larsen A and B Ice Shelves and inflow
glaciers from the peninsula, based on time series of radar satellite images and
numerical modeling. Particular emphasis of the presentation is on temporal
changes of ice flow of Larsen B and of the related glaciers. The pattern of retreat
and disintegration of Larsen B, with acceleration of ice flow previous to the
collapse, as well as the behavior of the glaciers after the collapse, is very similar to
that of Larsen A. After acceleration and rapid frontal retreat during the first few
years after the collapse, the glacier fronts retreat at slower rate, and the terminal
velocities started to slow down. This suggests that the glaciers will eventually
approach a new equilibrium as observed for retreating tidewater glaciers in other
regions. The analysis of the satellite image time series shows also further retreat of
the remnant section of Larsen B, as for example the calving of a major tabular
iceberg in February 2006. This calving event and the drift of the iceberg during the
first few days show major impact of ocean currents, as also observed in time series
of radar images for the disintegration events of Larsen A and B.
For interpretation of the dynamic response of the ice shelf a numerical model
solving the continuum-mechanical equations by means of finite differences was
applied. The model also considers influences of tensional and shear fractures on
the flow regime. Input data are obtained from flow fields of satellite data and field
measurements. In addition, the patterns of rifting and calving events as well as the
oceanographic boundary conditions seem to play a crucial role for the retreat and
disintegration of the ice shelf.
The influence of extra-tropical, atmospheric zonal wave three on the
regional variation of Antarctic sea ice
Marilyn Raphael (Invited Speaker)
This research deals specifically with the response of Antarctic sea ice concentration
to zonal wave three, the asymmetric component of the large scale atmospheric
circulation associated with meridional flow in the Southern Hemisphere. A zonal
wave 3 index (ZW3) is created from the NCAR-NCEP Reanalyses, 1979-2004 and
used to explore the influence of the large-scale atmospheric circulation on
Antarctic sea ice concentration (SIC).
15
Results indicate that this index is strongly associated with the empirical orthogonal
functions of SIC, which isolates the simultaneous variation in the three regions of
sea ice production around Antarctica - the Weddell and Ross Seas and the Amery
ice shelf. The index is also strongly associated with sea ice variability in the region
ranging from the west Antarctic Peninsula to the Bellingshausen-Amundsen Seas.
The relationship is most strongly expressed in the southern late fall to early winter
and is discussed in terms of the surface temperature and sensible heat flux
anomalies associated with ZW3. The amplitude of ZW3 increased over the
decades of the 1980s and 1990s. The influence of this change in amplitude on
Antarctic sea ice concentration trends is also discussed.
Using drifting icebergs as proxies for studying climate change
effects on ice shelves: the ICETrek Project
T. Scambos, D. MacAyeal, R. Ross, R. Bauer, Y. Yermolin, J. C.
Quinteros, D. Long, P. Skvarca, J. Thom
Tabular icebergs in the vicinity of the northern Antarctic Peninsula show in most
cases a rapid drift to the northeast, across the Scotia Sea to South Georgia Island.
During this drift, their climatic and oceanographic environment changes
significantly. In two recent cases, of seven studied, large icebergs experienced
break-up events similar to those of the Larsen A, Wilkins, and Larsen B ice shelves
(events of 1995, 1998, and 2002, respectively) as they endure successively warmer
ocean and air conditions. The icebergs respond to these conditions in several ways,
and in particular significant differences are seen among icebergs in colder water
(within sea ice) versus bergs that are north of the sea ice edge. Laser altimetry from
ICESat shows that the bergs thin at rates up to 50 m/yr when north of the sea ice,
and less than approximately 10 m/yr south of it. Edge-wasting rates increase as
well. Moreover, bending forces at the ice edge change from dominantly convex-up
to concave-up, associated with the formation of an ice bench below the water line
as warmer surface waters are encountered. Significant changes are seen in
backscatter as the iceberg firn rapidly evolves via warming and melt percolation,
culminating in the formation of ponds or water-soaked firn on the surface, and
rapid disintegrating break-up. It is noted, however, that no shelf or iceberg thicker
than approximately 200 m has disintegrated in this fashion, so a combination of
precursor characteristics may be required.
In February and March of this year, research teams visited three icebergs in the
northwest Weddell Sea, and installed automated observing systems on two of
them. Small icebergs north of the ice edge in February in the vicinity of Marambio
Station show extensive surface fracturing suggesting whole-berg flexure by longwavelength ocean swell, and subsurface ice benches. Surface snow was extremely
coarse 'corn snow', actively melting at the time of observation, with audible
flowing water in the subsurface. Further south, a 12x13-kilometer iceberg, visited
later in the season, had recent warm but fine-grained snow accumulating over
coarse 'summer' firn and re-frozen melt layers. At the ice edge, a convex-up profile
was confirmed, and no ice bench or cavernous edge-wasting was seen. A third,
very large, iceberg (A22A, derived from the western Filchner Ice Shelf in 1986)
was visited in mid-March, just north of the ice edge. Here, firn conditions
suggestive of modification by rainfall and/or melt ponding were observed. Snow
pit density measurements indicated a range of 0.5 to 0.6 with many ice layers.
16
An 11-meter ice core revealed an intense near-surface thermal gradient, indicating
surface winter-onset cooling (0 - 0.5 m), a very warm summer thermal wave (1.0 5.0 m) and a steep gradient to very cold temperatures (-15.1°C at 11 m). A partial
ice bench and extensive cavernous erosion were observed at the edge.
The in-situ automated systems (AMIGOS: Automated Met-Ice-Geophysical
Observation System) use steerable digital cameras, GPS, and simplified radio-echosounders to provide on-going data collection during drift and evolution of the
icebergs. The systems were placed approximately 2.5 km from the iceberg edges so
that edge observations could be made after anticipated edge-wasting occurs during
northward drift. Flag lines were set (200 m spacing, 1 to 2.2 km) towards the berg
edge to observe ice edge flexure. Additionally, accumulation and ablation stakes
were set for camera observation. The systems are intended to survive until close to
berg break-up, which is expected to occur in the next austral summer or shortly
thereafter. Initial results show the flag line experiment is promising, GPS-derived
ice motion is very closely associated with tidal forcing, and radar echo traces may
require extensive post-processing because of interference by the metal structure of
the AMIGOS station.
Long-term temperature trends in Antarctica: the view from ice cores
David Schneider
There have been several investigations of surface temperature changes across the
Antarctic, but these are limited by the instrumental records which generally extend
back only to the IGY. Obvious contrasts in trends between the Peninsula region,
where major warming has been observed, and the rest of the continent, where
some cooling has been observed, have been noted by several studies. Here, I
present results from an ice core based reconstruction of temperatures over the
continent. From the comparison with the long instrumental record from Orcadas,
it is evident both the Peninsula and the continent warmed over the 20th century,
although the Peninsula at a much greater rate. Interannual to decadal-scale
variability in the records is clearly tied to the Southern Hemisphere Annual Mode.
Another point of comparison is with the mean global temperature record – while
the reconstruction of continental temperatures shows a predominantly in-phase
relationship with the global record, the Orcadas record shows no clear
relationship, suggesting the importance of regional processes in driving the
observed changes.
I also seek collaboration on a synthesis of high-resolution ice core data from across
the Antarctic and elsewhere to be used in conjunction with water stable isotope
modeling.
Reconstruction of the firn thermal processes from the firn
temperature measurements
Olga Sergienko, Douglas R. MacAyeal, Kelly M. Brunt, Laurence Mac
Cathles
Disintegrations of Larsen Ice Shelf A and B in 1995 and 2002, respectively, were
preceded by two decades of extended summer melt seasons. The presence of melt
ponds on the both Larsen A and B immediately before their collapses suggests a
strong connection between surface melting and break-up events. Thus, monitoring
of ice-shelf surface melting is required for the ice shelf stability estimations.
17
Large tabular icebergs, which recently calved from the various Antarctic ice shelves
and drifted north, can be considered natural experiments depicting the ice shelf
behavior under warming conditions. Therefore, the observation of surface melting
on icebergs is essential. During the Austral summer 2004-2005 a field study of
surface melting was undertaken on iceberg C16 (Ross Sea). Twelve thermistors
were installed in 2.5 m subsurface layer for continuous firn temperature
measurements. Two 4.5 m firn core were extracted during two successive field
seasons (2004-2005 and 2005-2006). Analysis of the core densities shows
increasing surface melting during 2005. Thermistor temperature data is used to
reconstruct thermal processes in the firn subsurface layer.
Meridional circulation between the Antarctic Peninsula and
southeastern South America: cold surges one way and biomass
burning emissions the other way.
Alberto Setzer, Francisco E. Aquino, Marcelo Romao O.
In this paper we present two meridional circulation patterns in the lower
troposphere between the north of the Antarctic Peninsula (AP) and South America
(SA) that occur in all seasons of the year, so far not yet presented in the literature.
Low pressure systems in the Weddell Sea produce outbursts of cold air at surface
level that protrude 60° of latitude northwards, causing temperature declines of
10°C and precipitation in tropical areas in southeast and east SA. In the opposite
direction, southward flow from central SA reaches the north AP under high
pressure ridges, causing temperature increases of also 10°C or more. These
meridional flows are corroborated with plenty of evidence of observational data
from weather stations in the north of the AP and southeast SA, satellite imagery,
synoptic charts, and with aerosol sampling in the South Shetlands.
Melting and freezing beneath the Larsen Ice Shelf
Andrew Shepherd, Zhijun Du, Andreas Vieli (Invited Speaker)
We use interferometric synthetic aperture radar (InSAR) data recorded by the
European Remote Sensing (ERS) satellites to determine velocity changes of the
Larsen B ice shelf and its tributary glaciers. Because the precision of velocity
mapping is affected by the action of tide, we correct the velocity data for tidal
effects using an adaptive prediction from the AntPen tide model. By differencing a
series of InSAR pairs, we derive ice shelf and glacier velocities and grounding line
locations in 1995 and 1999. Assuming the ice shelf is floating in hydrostatic
equilibrium, we model ice thickness and density at each mapped velocity grid point
using point measurements of ice thickness within the BEDMAP database and a
spatially continuous model of surface elevation derived from satellite altimetry. We
combine the InSAR velocity data, ice thickness model, and a time series of ice
thickness change to determine the rates of ice melting and freezing at the ice shelf
base at each epoch, assuming mass continuity.
18
Satellite-Derived Changes of the Larsen C System from ICESat and
MODIS Data
Christopher A. Shuman, Ted A. Scambos, Mark A. Fahnestock,
Christina L. Hulbe
The remaining ice shelves of the Antarctic Peninsula are a challenging but essential
target for remote sensing studies. Recent observations of outlet glacier response to
loss of the Larsen B ice shelf indicate that ice shelves play an important role in
regulating glacier flow, at least in the terminal region. Once collapse occurs,
acceleration and associated thinning at the glacier terminus can propagate
upstream, sending formerly grounded ice into coastal waters and contributing to
sea-level rise. It is thus important to evaluate the collapse potential of the
Peninsula’s remaining ice shelves. These “at risk” ice shelves, are now being
monitored using ICESat laser altimetry data overlaid on temporally-similar imagery
from MODIS. Thinning, thickening, crevassing, extension, and calving can all be
monitored by these repeated satellite observations.
The Larsen C ice shelf, the largest in the Antarctic Peninsula is specifically targeted
in this project. The Larsen C ice shelf is located in an area that is experiencing a
regional temperature increase, has a mean January temperature of about -1.5°C,
has very high radar backscatter, and experiences a melt season of about 50 days
duration. Extensive meltwater ponding, a key characteristic of the Larsen A and B,
and other shelves before disintegration, is not currently observed on this ice shelf.
The ICESat data currently available is well positioned for monitoring the Larsen C
ice shelf. Approximately 20 ground tracks (ascending and descending) of the
current operations plan have been repeatedly profiled in 2003-2005 across this
feature and these elevation profiles are located nearly perpendicular to flow across
the area. Although cloud cover, potentially causing significant gaps and/or
anomalously low elevations, is a concern, the available ICESat data provides
critical measurements of the surface elevations and their change with time across
the Larsen C ice shelf. The MODIS data ensures the best interpretation of the
available elevation data across specific changing features, and also helps identify
cloud impacts.
Signals of climatic variations in the northern most part of the
Antarctic Peninsula and the South Shetlands Islands
Jefferson C. Simões, Francisco E. Aquino, Alberto W. Setzer, Jorge
Arigony-Neto, Siclério Ahlert, Ulisses F. Bremer, Cláudia D. Beck,
Norberto Dani (Invited Speaker)
This paper explores climatic and cryospheric data sets to examine signals of
climate variations in the extreme north of the Antarctic Peninsula (north of 64° S)
and its offshore islands. Glaciers and ice caps of four islands (Brabant, Joinville,
King George, and Nelson) show a non-uniform reduction for the period 19562001. For example, King George Island (KGI) has lost 7.1% (89 km2) of its ice
cover since 1956. On the other hand, on Nelson Island, separated from the former
island by a narrow strait, the amount of ice lost is almost imperceptible. Further
south and nearer to the Antarctic Peninsula, Joinville Island’s loss is also restricted
(0.6% of a total area of 1477 km2, from 1990 to 2000). Glacier retreat on these
three islands shows a clear general pattern: ice loss occurred mainly in outlet
tidewater glaciers flowing to the southeastern coasts and mainly in bays and other
well protected areas. On the other hand, in mountainous and irregular Brabant
Island, no glacier retreat has been detected from 1989 to 2001.
19
Having this in mind, we considered the influence of sea occurrence in bays and in
other sheltered coasts. At least at Admiralty Bay (KGI), sea ice cover area
decreased from 1977 to 1999. This trend was concomitant to an air temperature
and wind speed increase and a greater frequency of northerly and north-westerly
winds, advecting relatively warmer air masses from lower latitudes. On the other
hand, the greatest amount of ice loss in Admiralty Bay (22 km2 since 1956)
occurred before 1980. Rather than a common response to an observed general
atmospheric warming trend (0.022°C a-1 from 1948 to 1995 in Admiralty Bay),
glacier retreat in the region results from an interplay of ice front and coast
morphologies, sea ice extent and variations in other climatic parameters such as
precipitation. Further, from 1998 to 2005, the mean annual air temperature
declined about 1°C.
A century of climate change on the Antarctic Peninsula
Susan Solomon, David W. J. Thompson (Invited Speaker)
The Peninsula has special places in Antarctica’s past and in its present, and both
will be described in this talk. The first expedition to winter-over in the Antarctic
spent 1898-1899 locked in the grip of sea ice near its coastline. That remarkably
international team made pioneering measurements of the climate through that first
'Antarctic night'. The crew, their experiences, and their data will be briefly
reviewed. Just over a century later, evidence of systematic climate change in this
region is now available. The Antarctic continent holds a unique place in the world
as the sole large region not experiencing warming over much of the interior, while
parts of the Peninsula display enhanced warming in certain seasons. Much of this
behavior has been explained through improved understanding of changes in the
atmospheric circulation and related parameters linked to the Southern Annular
Mode (SAM), which in turn are driven in part by ozone depletion and Antarctica’s
unique ozone hole. Changes in ozone, greenhouse gases and other factors that are
currently making Antarctica’s climate distinct from the land first explored a century
ago will be reviewed.
Trends in sea ice retreat and subsequent advance in response to
ENSO and SAM variability
S. E. Stammerjohn, D. G. Martinson, R. C. Smith, X. Yuan
The Antarctic Peninsula (AP) region is rapidly warming, ice shelves and marine
glaciers are retreating, and winter sea ice duration is decreasing. Elsewhere in
Antarctica and the Southern Ocean, climate trends are weak or indicate cooling. In
an attempt to understand the mechanisms of climate change in the AP region, we
first identify when and where the most profound sea ice changes in the Southern
Ocean are occurring, then we explore how the physical system is sensitive to these
changes. Towards this objective, newly analyzed data reveal strongly opposing
trends in the timing of annual sea ice retreat (November - February) and the
subsequent advance (February - May) in two regions of the Southern Ocean. Sea
ice is retreating earlier and advancing later in the southern Bellingshausen Sea,
resulting in a decrease of 80 ± 13 annual sea ice days over 1979-2002. In the
western Ross Sea, opposite trends have resulted in an increase of 55 ± 12 annual
sea ice days. An intensification of the high latitude response to La Niña (more so
than to El Niño) during the spring-to-autumn period in conjunction with increased
polarity of the Southern Annular Mode (SAM) help to explain both the
intensification and localized nature of these opposing sea ice trends.
20
Additionally, inter-seasonal feedbacks help to explain the amplified winter
warming in the Antarctic Peninsula region: changes occurring in the atmospheric
circulation during austral spring, summer and autumn are negatively affecting the
advance and retreat such that winter sea ice duration, concentration and thickness
are decreasing, and ocean winter heat flux is increasing; these changes in turn
amplify the increase of air temperature in autumn and winter.
Glaciological evidence for abrupt climate change: past and present
Lonnie G. Thompson, Ellen Mosley-Thompson (Invited Speaker)
It is essential to determine whether the abrupt climate changes underway in the
Antarctic Peninsula (AP) over the past few decades reflect, in part, a response to
anthropogenically driven, globally averaged warming or whether they lie within the
natural range of past climate variability. Records providing the necessary time
perspective may be reconstructed from chemical and physical properties preserved
in the regional ice cover and ocean sediments. Comparisons are made among the
geographically dispersed, annually dated ice cores records from the Antarctic
Peninsula, the tropical Quelccaya ice cap (Peru) and Bona-Churchill (southeast
Alaska) over the past 500 years. Decadally averaged δ18O histories demonstrate
that the current warming at high elevations in mid- to low-latitudes is
unprecedented for at least the last two millennia. Is this the case for the Antarctic
Peninsula? Data to address this question are lacking.
A longer, multi-millennial time perspective from a variety of recording systems
suggests that an abrupt climate event, roughly 5000 years ago, was widespread and
spatially coherent throughout much of the tropics. A possibly contemporaneous
abrupt event is evident in the Ocean Drilling Project (ODP) 108 Palmer Deep core
magnetic susceptibility record (highest terrigenous sediment input and reduced
marine productivity) and is coincident with enhanced input of ice rafted detritus.
These observations suggest a very large scale mid-Holocene event in the Antarctic
Peninsula region. Moreover, the current melting of the ice fields on Kilimanjaro’s
summit is unprecedented in its 11,700 year ice core history just as the recent
collapse of the Larsen B Ice Shelf is unprecedented within the Holocene. These
data argue that recent and rapid climate changes in both the Antarctic Peninsula
and much of the tropics may be linked by common forcing mechanisms. Long,
high temporal resolution ice core histories from the Antarctic Peninsula are
essential to complement other proxy records in the region and to better isolate and
quantify the dominant processes forcing these climate and environmental changes.
Recent decades of climate and cryospheric change on the Antarctic
Peninsula
David Vaughan, Hamish Pritchard, Alison Cook, Adrian Fox, Jane
Ferrigno
This talk will cover four examples of recent changes in the cryosphere of the
Antarctic Peninsula; each of which has been significantly advanced since the
meeting, "Antarctic Peninsula Climate Variability: History, Causes and Impacts"
(Cambridge, 2004). We use a new analysis of meteorological data to show clear and
significant trends in surface melting conditions over the last 50 years. We use
satellite imagery, aerial photography, and survey data to chart the course change in
length of approximately 244 glaciers over the last 61 years, and demonstrate a
strong trend toward glacier retreat over this period.
21
We use Satellite SAR images to monitor the velocity of these glaciers over the last
ten years, and find a clear pattern of increase in glacier velocity of around 10%.
Finally, we record the demise of Jones Ice Shelf over the last 30 years. The
examples demonstrate that the recent changes in climate on the Antarctic
Peninsula are having a dramatic impact on the extent or dynamics of the ice sheet
– arguably the only demonstrable impacts of contemporary climate change on the
ice sheet of Antarctica – but also that the changes could continue, given only
modest rates of summer warming. We will discuss the likelihood that such changes
will continue, or accelerate, in coming decades, and their potential to make a
substantial contribution to sea-level rise.
Poster Presentations
The sub-Antarctic atmospheric circulation between 15° W and 90° W
and its effects on the climates of the Antarctic Peninsula and
Southern South America
Francisco Eliseu Aquino, Alberto Setzer, Jefferson Cardia Simões
Surface air temperature increases of up to about 3°C in the last 50 years have been
recorded in the western coast of the Antarctic Peninsula (AP). Following worldwide tendencies, temperatures in continental South America have also increased in
the same period, but to a much smaller extent; southern Brazil shows for the same
half century an increase of 0.4°C, which for the last 20 years amounts to less than
0.2°C. Most studies have focused on global and hemispherical atmospheric
circulation patterns and indices averaged over seasons and years during long-term
periods to explain the temperature variations in the AP.
This paper considers specifically the longitude sector of 15° W to 90° W and
shows that an important regional context in the scale of days can have marked
effects in the temperatures of AP and in south South America as a result of
meridional flows at surface level that result from synoptic systems in the region.
Analyzing observational data for the period of 2004-2005 we show that cool and
rainy spells in southeast South America result from the outflow of Weddell Sea
surface air, and that increases of 10°C are common in the South Shetland Islands
under northern flow from South America. The latitudinal position of the subpolar
jet stream is one of the key factors in such synoptic configurations, and the further
north it is located, the warmest temperatures are found in the north AP. An
extended investigation for a period of 40 years to detail this meridional flow is
under way to evaluate its effects in the warming records of AP temperatures.
A spatial database in support to glaciological research during the
International Polar Year 2007-2008
Jorge Arigony-Neto, Steffen Vogt, Ricardo Jana, Frank Rau, Helmut
Saurer, Jefferson C. Simões, Hermann Gossmann
In the framework of the international project Global Land Ice Measurements from
Space (GLIMS), a glacier inventory of the Antarctic Peninsula was established. The
GLIMS objectives are to monitor glaciers on the Earth using primarily satellite
data. The Department of Physical Geography of the University of Freiburg is
integrated in GLIMS as the Regional Center (RC) for the Antarctic Peninsula.
22
As the Antarctic Peninsula covers a large region extending from approximately 60°
S/55° W to 75° S/80° W, the RC Antarctic Peninsula cooperates with several
international scientific and administrative institutions. These partners are
responsible for the analysis of glaciers in specific sub-regions of the research area.
To record and manage results from satellite image analyses on glaciers on the
Antarctic Peninsula and to administer metadata describing such analyses, we
implemented a glacier database containing data on more than 950 glaciers. The
relational database design is compatible with the GLIMS data transfer standards
and was developed using free and open source software. The semantics are
compliant with the GLIMS data dictionary and the Scientific Committee on
Antarctic Research (SCAR) Feature Catalogue. It enables full compatibility with
the GLIMS central database and the emerging Antarctic Spatial Data
Infrastructure (AntSDI). Furthermore, the relational structure of the database
facilitates the record of additional cryospheric data resulting from further projects.
Web access interfaces have been developed both for human interaction and for
machine to machine communication. A browser-based interface allows users to
query the glacier data base using text search or through interactive maps. The
machine-to-machine accessibility is based on open web services implementing
Open GIS Consortium (OGC) specifications and relevant ISO TC211 standards.
Querying and retrieving spatial features and their attributes through an OGC Web
Feature Service (WFS) interface for example enables interoperability with other
OGC compliant applications such as GIS packages or spatially enabled data
mining tools at the feature level.
In this paper, we describe the structure and functionality of the Antarctic Peninsula
Glacier Database and its web based interfaces. In addition, we give examples of
using the database to support glaciological research during the International Polar
Year 2007-2008.
Improving glacier surface models for mass balance assessment
using laser scanning and aerial imagery – implications for
reconstruction of recent Antarctic Peninsula mass change
Nicholas E. Barrand, Tavi Murray, Timothy D. James, Stuart L. Barr,
Adrian J. Fox
This research is presented as an analogue case study for future analyses of
Antarctic Peninsula ice masses. Airborne laser scanning and digital aerial
photogrammetric techniques may be combined to provide high-quality, highresolution surface models for measuring changes in glacier mass balance. A data
set of airborne laser data acquired over Midre Lovénbreen, Svalbard, is shown to
provide elevation information accurate to 0.17 m root mean square over the glacier
surface. Although the repeatability of laser data degrades over very steep
mountain-sides and peaks it is possible to extract large numbers of ground control
points from surrounding bedrock features. In the case of Midre Lovénbreen, a
small (approximately 4 km long) polythermal-type valley glacier, more than 70
ground control points can be identified using laser return intensity information and
3-D data visualization techniques. Elevation models are produced using digital
photogrammetry from a block of 19 overlapping vertical stereo photographs
imaged concurrently with the laser data. Comparisons of photogrammetricallyderived models with a laser data derived 'base' model show that marked increases
in DEM quality are achieved with the addition of extra ground control data.
23
Models are generated using a set of historical vertical aerial photographs of the
glacier and surrounding areas from 1966. Changes in frontal position and the
volume, and hence mass balance of the glacier between 1966 and 2003 are given.
The availability of historical aerial photographs of parts of the Peninsula along with
high-quality elevation information from NASA's Ice, Cloud and land Elevation
Satellite (ICESat) offers the possibility of combining laser data and aerial imagery
in a similar way (e.g. Schenk et al., 2005). This approach has the potential to extend
the temporal record of surface topographic change significantly further back in
time than is possible using current altimetry measurements.
The ADELIE project: Antarctic Drifter Experiment; Links to Isobaths
and Ecosystems
Karen J. Heywood, Sally E. Thorpe
In January-February 2007 we will undertake a hydrographic section, float and
drifter deployment at the tip of the Antarctic Peninsula as part of the ADELIE
project. Recent data suggest that, contrary to prevailing views, there are pathways
for near surface currents around the Antarctic Peninsula to the west. If proved,
these would be important for the retention and/or dispersal of krill larvae and
other passive drifting particles. The Antarctic Slope Front appears to lose its
properties as it enters the Weddell Scotia Confluence. These pathways will be
mapped by deploying surface drifters and Argo floats to the southeast of the tip of
the Antarctic Peninsula, spanning the Antarctic Coastal Current and Antarctic
Slope Front into the Weddell Sea. A CTD/LADCP section across these flows will
indicate their locations and transports. Output from eddy resolving ocean models
will be analysed and virtual drifters deployed in their flow fields. The influence of
bathymetry controlling the splitting and steering of these frontal jets will be
studied. The poster will describe the background to the project and the fieldwork
planned for 2007.
Investigation of King George Island climatology
Victor Lagun, Nikolay Ivanov, Svetlana Jagovkina
Recent numerical estimations of climate variability parameters for the Southern
Hemisphere indicate that the Antarctic Peninsula region is a main hemispheric
“hot spot.” This phenomena is traced in surface and troposphere warming trends,
in prevailing large-scale circulation form, surface pressure decreasing, in sea ice
retreat tendency, ozone decreasing, Antarctic Circumpolar warm water
propagation over the Peninsula’s shelf, in appearance of natural emissions of
greenhouse gases from ornitogenic soils at sub-Antarctic Islands, in lichen and
penguin area systematic change, and so on. However, the Climate and General
Circulation Models based on modern atmospheric trace-gas content scenarios are
not able to reproduce evident warming conditions near the Antarctic Peninsula.
Therefore, the study of current and historic regional climatic variations based on
observed data is very important for numerical model development using different
relationships between the Antarctic Climate System parameters. Some ideas for
physical-processes parameterization can be obtained from diagnostic estimates of
the Antarctic Climate System parameters distribution and from their variability.
The King George Island (KGI) climate variability pictures based on manned
stations data completed with SCAR READER (REference Antarctic Data for
Environmental Research) Projects and SCAR King George Island Working Group
information resources are presented.
24
The results of the probabilistic analysis of a comprehensive time series of surface
air temperature and air pressure at sea level in this region undertaken for
determining the interannual variability characteristics showing the annual cycle
modulation by synoptic scale variability are demonstrated. Current meteorological,
upper air sounding, solar radiation, ozone, hydrological, sea ice, biological and
greenhouse gas concentration data for total measurements period are used for
unique local climate regime formation description. Interannual tendencies of
seasonal surface and tropospheric temperatures over King George Island are more
prominent than those observed in continental Antarctica. Three IPY Project
(CLICOPEN, ANTPAS and COMPASS) plans related to KGI natural complexes
investigation are discussed.
Glacier behavior after ice shelf collapse in Crane Glacier, Antarctic
Peninsula
Amie Lamb, Christina Hulbe, Ted Scambos, Jennifer Bohlander
Since the early 1990s, many changes have been observed in the Antarctic
Peninsula’s glacier systems, presumably in response to warming of about 2.5 C
over the last 60 years. One such change, the speed-up of Crane Glacier, is of
interest here. Crane is a large glacier on the eastern side of the Antarctic Peninsula
that began to speed up in 2002, after the disintegration of the Larsen B ice shelf
into which it had flowed. We use a combination of satellite remote sensing data
sets to study this change. Glacier velocity is measured using standard imagecorrelation techniques and Landsat 7 and ASTER images. Speeds in the
downstream trunk of the glacier were significantly slower between 18 December
2002 and 20 February 2003 (summer) than speeds computed over the entire 392day period between 18 December 2002 and 13 January 2004. No significant
differences were observed in the upstream region of the glacier. Calculated speeds
due to internal deformation of the ice are significantly smaller than the observed
speeds. Together, these lines of evidence suggest that the glacier is sliding over its
bed during at least part of the year. The relatively slow summertime speeds
(compared to the annual speed) may indicate that by this time in the melt season,
the basal water system has become efficient, and basal water pressures a lower than
at other times of the year. If this interpretation is correct, it suggests that in the
absence of the Larsen B, Crane Glacier is behaving as a tidewater glacier.
Holocene paleoceanography recorded in a sediment core from
South Orkney Plateau
Jae Il Lee, Ho Il Toon, Kyu Cheul Yoo
A 533 cm-long gravity core sediment retrieved from the northwestern end of the
South Orkney Plateau, West Antarctica, records high-resolution information on
changes in oceanographic process and paleoclimate that occurred during the last
8,700 years. Age of the sediment was determined by accelerator mass spectrometry
radiocarbon dating for organic matter in six sediment samples including one seafloor sediment sample from box-core top, which shows very old reservoir age of
approximately 2900 radiocarbon years. Sedimentation rate varies between 46 and
84 cm/kyr with an average of 61 cm/kyr. Content of biogenic opal ranges from 18
to 31%. Detailed geochemical analyses (content of total organic carbon (TOC),
C/N ratio, and content of biogenic opal (BSi)) and grain size analysis indicate that
major shift in the content and nature of organic matter had occurred between 5750
and 4480 yr BP.
25
Highly variable TOC, high C/N ratio, and high BSi/TOC ratio of the lower part
of the core implies that this area was under the influence of Scotia Sea water until
5750 yr BP. High TOC, low C/N ratio, and low BSi/TOC ratio of the upper part
suggests increased influence of Weddell Sea water in the area since 4480 yr BP. We
suggest that northward shift of Weddell-Scotia frontal system occurred between
5750 and 4480 yr BP, and it marks the onset of Neoglacial condition in the South
Orkney Plateau.
Characteristics of tephra in Holocene lake sediments on King
George Island, West Antarctica: implications for deglaciation and
paleoenvironment
Hyoun Soo Lim, Yong Il Lee, Ho Il Yoon, Andrzej Tatur
Several reworked tephra layers in gravity-flow deposits are present in lacustrine
core sediments collected from Hotel and Rudy lakes on King George Island, South
Shetland Islands, West Antarctica. The tephra record is more abundant in a long
Hotel Lake core (515 cm long). In this study, the morphology, grain size
characteristics and composition of volcanic glass samples from five tephra layers
(A, B, C, D and E) of Hotel Lake and from one (R) of Rudy Lake were examined
to characterize the eruptive mechanisms that produced them and to test the
suggestions that they were derived from Deception Island.
Two distinct types of tephra were identified on the basis of color, vesicularity and
morphology: the dominant, pale to dark brown basaltic shards and the minor,
light-colored pumice shards. The relative proportions of basaltic and pumice
pyroclasts are different from sample to sample, and both types have various
degrees of vesicularity. Concentrations of major elements were analyzed with
electron microprobe. The analyzed tephra samples show the wide range in
composition from basalts to rhyolite magmas with medium-K tholeiites, though
there is a predominance of basalts and basaltic andesites. Therefore, the tephra
samples were divided into basic and silicic glass populations. The basic tephras
occur in all studied horizons, but the silicic tephras present in only three layers in
the Hotel Lake (A, D and E). The silicic tephras can be divided into two groups:
rhyolitic tephra with high- and low-K content. The geochemical similarity between
glasses in individual tephra layers was compared using the similarity coefficient as a
discriminator. Similarity coefficients (SC) were calculated for basic and silicic
tephras separately. Based on the very high SC (0.95-0.99), A, B, C and R tephras
are geochemically indistinguishable from one another, and thus are considered
equivalent. The same is true for D and E tephras. SC values for silicic tephra in A,
D and E are relatively low from 0.84 to 0.92. However, all the rhyolitic tephra with
high-K content in A, D and E tephra samples have SC values larger than 0.96,
suggestive of geochemical equivalence. The presence of such geochemically
equivalent tephras suggests that they were the product of single volcanic eruption
event and reworked in different times.
Most of the basic tephra probably represent products of explosive eruptions of
Deception Island, the most active subaerial volcano in the Antarctic Peninsula
region. Less than 20% of tephra belongs to silicic glass and occurs in three tephra
horizons of Hotel Lake. However, source volcano(es) for about 10% of basic
tephra and silicic tephra are not readily identified from nearby volcanic centers.
26
Except for the studied tephra in Rudy Lake, all tephra samples in Hotel Lake are
not ashfall deposits but reworked and redeposited pyroclasts derived from
retreating ice sheet, resulting in the occurrence of geochemically equivalent tephra
samples in different tephra horizons. The dating of the studied tephra horizons
represents the timing of deglaciation rather than that of volcanic eruptions. The
result of this study implies that combined with sedimentological information more
chemical criterion is necessary to study tephrochronology and regional correlation
and to understand paleoenvironmental changes using tephra.
Sea-swell induced vibration of ice shelves: an iceberg calving
mechanism capable of trans-oceanic connections?
Douglas MacAyeal, Kelly Brunt, L. Mac Cathles
Over the past 3 years, we have deployed broad band seismometers on the Ross Ice
Shelf, Antarctica, and various icebergs recently calved from this ice shelf (B15A
and C16), to investigate the effect of sea swell on bobbing, rocking and pitching
motions that contribute to the calving process. Our observation reveal a curious,
unexpected relationship between storm activity in the distant North Pacific and
swell induced vibration along a wide swath of Antarctica’s calving margin. The
implication of our observation is that intensity variations of storms within the
usual storm tracks of the global circulation system can influence far-separated ice
sheets in a nearly synchronous manner. This influence offers a possible clue
toward understanding how iceberg calving in the glacial North Atlantic may
respond to atmospheric triggers, and further highlights the role of sea swell as an
environmental process capable of influencing climate. A future observation that
we recommend for study of ice-shelf disintegration along the Antarctic peninsula
will be the deployment of broadband seismometers on various parts of the Larsen
and Ronne ice shelves to determine the extent to which sea-swell generated in the
far North Atlantic, as well as in the close field environment of the Weddell Sea, has
an impact on ice-shelf fragmentation and breakup.
The dynamics of palaeo-ice streams draining the Antarctic
Peninsula Ice Sheet during the Late Quaternary
Benedict Reinardy
Multibeam bathymetric data, sub-bottom profiler (TOPAS) data and sediment
cores had been collected from the NE Antarctic Peninsula continental shelf on
cruise JR71 of the RRS James Clark Ross. The data sets had been used to
reconstruct the flow-dynamics of the Antarctic Peninsula Ice Sheet (APIS) since
the Last Glacial Maximum (LGM). Highly attenuated bedforms in an acoustically
transparent sedimentary unit were observed in several cross-shelf troughs
documenting that the APIS was drained by ice streams flowing towards the shelf
break. Some areas are characterized by cross-cutting bedforms suggesting a change
in ice flow direction since the LGM, possibly during the deglaciation. Cores
recovered from the bathymetric troughs indicate a stiff till overlain by a soft till.
The availability of sediments at the seabed may have facilitated the development of
a deforming till layer. The aim of this research is to interpret the varying bed
conditions below ice grounded on the shelf NE of the Antarctic Peninsula since
the LGM, particularly during APIS retreat. 3D mapping of Robertson Trough
from TOPAS and multibeam bathymetric data along with sediment cores will be
carried out. The micromorphology of sediment samples taken from the cores will
be analyzed to reconstruct the different bed conditions responsible for the
deposition of the soft and the underlying stiff till.
27
The change in ice source documented by the cross-cutting bedforms in some areas
and its relationship to ice streaming will be further investigated. Geomagnetic
palaeointensity measurements will be used to date both the timing of ice retreat
and to discover whether ice streaming occurred during deglaciation. Particular
attention will be paid to distinct sedimentary wedges on the shelf, which are
interpreted as grounding line still stands during overall APIS retreat.
Quaternary deglaciation of the South Shetland Islands, Antarctica
Yeong Bae Seong, Hyoun Soo Lim, Ho-Il Yoon, Yong Il Lee, Lewis
Owen
Knowledge of the past configurations and behavior of the West Antarctic Ice
Sheet (WAIS) is necessary to calibrate glaciological models that attempt to predict
future responses of the ice sheet and to quantify the contribution of the Antarctic
ice sheets to eustatic sea-level rise during the last deglaciation. The WAIS (West
Antarctic Ice Sheet) of Saalian-Illinoian age collapsed catastrophically during the
Eemian-Sangamon interglacial, to be followed by renewed ice-sheet growth during
the last glacial stage. This collapse caused a eustatic sea-level rise to about 6m some
120,000 years ago. Extended through Cenozoic era, the debate on Ice Sheet
stability cannot be far reached on a consensus. Antarctic ice sheet has remained
stable since middle Miocene time, whereas massive deglaciations occurred during
Pliocene and Pleistocene period. However, It is likely that traces of interglacial
landforms and sediments within the sphere of the WAIS have been destroyed or
obscured during the most recent stage of expansion. This is why there is as yet no
unequivocal geomorphological evidence for large-scale melting of the WAIS
during the last interglacial, excepting marine-geophysical and sedimentological
works. Possibly it is more noteworthy to search for such remnants either on the
coasts of Antarctic Peninsula or on the sub-Antarctic islands of the Scotia Sea
beyond the present northern limits of shelf Ice. We propose here to investigate the
raised beach sediments in the South Shetland Islands in order to test the
hypothesis. We will undertake geomorphic mapping and collect samples for
cosmogenic radionuclide and optically stimulated luminescence dating. This work
will lead to define the timing and configuration of former deglaciation of the
WAIS and help us model the future behavior of the WAIS in light of global
eustatic sea-level change.
Climate tendencies in the South Shetlands: was 1998 a climate
divider?
Alberto Setzer, Francisco E. Aquino, Marcelo Romao O.
Temporal series of meteorological data for the South Shetland Islands in widely
distributed data basis show air temperature increase and pressure drop at surface
level during the last decades. These patterns are particularly clear in reanalysis data
that start in 1948, and a large number of papers is found describing and
interpreting these tendencies, and using them to support future scenarios and to
correlate them with assorted environmental variables. However, a closer look at
more recent station records in the region present a puzzling contradiction to the
long term series and reanalysis tendencies. Surface pressure raised some 8 hPa in
the last 20 years and appears to be currently at a maximum; since 1998-99,
therefore for seven years, air temperature declined about 1oC. Surface winds in the
last years are also decreasing, as a possible indication of a change of weather
pattern in the region.
28
This paper presents the evidence to the contradictions in the data sets and points
to relevant effects in generating wrong analyses of Antarctic climate. For instance,
an incorrect reference of surface pressure results in wrong temperatures at
standard pressure levels in the atmosphere leading to non existing temporal
variations.
Plausible oceanographic interpretation on the recent rapid warming
trends of the South Shetland Islands
Kyu-Cheul Yoo, Ho Il Yoon
Marian Cove (3.5 km long and 1.5 km wide) is one of tributary embayments in
Maxwell Bay, King George Island, West Antarctica. King George Island, the
largest of the South Shetland Islands off the northern tip of the Antarctic
Peninsula (AP). The retreat rate of tidewater glacier of the cove is rapid up to
about 81 m/yr in more recent years (1988 to 2001) than the past (1957 to 1988)
(about 12.5 m/yr). The recent rapid trend has significant oceanographic
implications along with atmospheric change. We will present results of
hydrographic data (2000 and 2004) on a fixed station near the head glacier of
Marian Cove, and mooring results of temperature and salinity for two years (2004
to 2005).
Late Holocene cyclic glaciomarine sedimentation in subpolar fjord
of the South Shetland Islands, Antarctica and its paleoceanographic
significance: sedimentological, geochemical and paleontological
evidence
Ho Il Yoon, Kyu-Cheul Yoo, Young-Suk Park, Hyoun Soo Lim, BooKeun Khim, Sung Joong Kim
The glaciomarine sediment record of Maxwell Bay, South Shetland Islands (West
Antarctica), a large marine calving embayment, contains distinctive cyclic deposits.
Each glaciomarine couplet forms alternating clast-rich massive diamicton
deposited in cold climate by iceberg rafting detached from coastal fast ice in which
algal plants as well as sand and/or gravel were entrained and, in warmer climate,
meltwater deposits of weakly laminated mud with clast-poor stratified diamicton
deposited by iceberg rafting coming from the tidewater glaciers depleted in sand
and algal components. Although iceberg rafting occurs throughout the deposition
of the whole cores, organic matters are deposited in high concentration and forms
organic-rich massive diamicton only during cold condition because of minimal
dilution of silisiclastic particle by meltwater influx in Maxwell Bay. When the
meltwater discharge decreases in colder condition, and resultant biological
productivity was reduced on the surface water, ice rafting from the shorefast sea
ice along the coastal region might play an important role for transporting benthic
plants and/or coastal macroalgal components as well as loads of sediments and
dropstones, resulting in increased C/N ratio in clast-rich massive diamicton. AMS
radiocarbon analyses conducted on calcite shells in sediments revealed an excellent
chronology for the past 3000 years. Fluctuations in total organic carbon preserved
during cold period record approximately 4 cycles over the same time period, with
the average duration of cooling cycle being about 500 years. In spite of rarity in
southern hemisphere, this can be correlative with the high frequency (550 years)
variability in reduced NADW (North Atlantic Deep Water) production during cold
climatic conditions, as demonstrated for glacial periods throughout the
Pleistocene.
29
Late Quaternary sedimentary processes in the northern continental
margin of the South Shetland Islands, West Antarctica
S. H. Yoon, H. I. Yoon, K. C. Yoo
Sedimentary facies and high-resolution (3.5 kHz) echo facies were analyzed to
elucidate sedimentation pattern of the late Quaternary glaciomarine deposits in the
northern continental margin of the South Shetland Islands, West Antarctica. Six
sedimentary facies are classified based on grain texture and sedimentary structures
in gravity cores. The high-resolution echo characters are classified into 6 echo
facies on the basis of clarity, continuity, and shape of bottom and subbottom
echoes together with sea floor topography. Distribution of the echo and
sedimentary facies suggest that a large part of the continental margin deposits
formed during the Last Glacial Maximum (LGM) and subsequent glacier-retreating
period. When the grounded glaciers extended to the present shelf break during
LGM, coarse-grained subglacial tills were widespread in the shelf area, and deep
troughs in the shelf were carved beneath the fast-flowing ice steam. As the glacial
margin retreated landward after LGM, dense meltwater plumes released from the
retreating ice-front were funneled along the glacier-carved troughs, and
accumulated channel- or canyon-fill deposits in the shelf and the upper to mid
slope. At this time, some upper slope sediments seem to have been rarely
reworked by slope failures and contour currents. After the glacial retreat,
sediments in the shelf and slope areas have been mainly introduced by persistent
(hemi) pelagic settling, and fine- grained turbidity currents frequently occur along
the axis of the South Shetland Trench.
30
Participants
John G. Anderson
Rice University
Houston, TX, USA
[email protected]
Francisco Aquino
Centro de Previsão de Tempo e Estudos Climáticos, Instituto Nacional de
Pesquisas Espaciais
Sao Jose do Campos, Brazil
[email protected]
Todd Arbetter
British Antarctic Survery
Cambridge, United Kingdom
[email protected]
Jorge Arigony-Neto
University of Freiburg, Department of Physical Geography
Freiburg, Germany
[email protected]
Nicholas Barrand
University of Wales Swansea, Department of Geography
Swansea, United Kingdom
[email protected]
Jennifer Bohlander
University of Colorado, National Snow and Ice Data Center
Boulder, CO, USA
[email protected]
Kelly Brunt
University of Chicago, Department of Geophysical Sciences
Chicago, IL, USA
[email protected]
Mac Cathles
University of Chicago, Department of Geophysical Sciences
Chicago, IL, USA
[email protected]
Eugene Domack
Hamilton College, Department of Geology
Clinton, NY, USA
[email protected]
William Fraser
Polar Oceans Research Group
Sheridan, MT, USA
[email protected]
31
Terry Haran
University of Colorado, National Snow and Ice Data Center
Boulder, CO, USA
[email protected]
Daniela Jansen
Alfred Wegener Institute for Polar and Marine Research
Bremerhaven, Germany
[email protected]
Ian Joughin
University of Washington, Polar Science Center
Seattle, WA, USA
[email protected]
Michèle Koppes
University of Washington, Department of Earth and Space Sciences
Seattle, WA, USA
[email protected]
Victor Lagun
Arctic and Antarctic Research Institute
Saint Petersburg, Russia
[email protected]
Amie Lamb
Portland State University
Portland, OR, USA
[email protected]
Jae Il Lee
Korea Polar Research Institute
Icheon, Korea
[email protected]
Amy Leventer
Colgate University
Hamilton, NY, USA
[email protected]
Hyoun Soo Lim
Korea Polar Research Institute
Incheon, Korea
[email protected]
Gareth Marshall
British Antarctic Survey
Cambridge, United Kingdom
[email protected]
Douglas Martinson
Lamont-Doherty Earth Observatory, Columbia University
Palisades, NY, USA
[email protected]
32
Robert Massom
Australian Antarctic Division and Antarctic Climate and Ecosystems Cooperative
Research Centre
Tasmania, Australia
[email protected]
John Maurer
University of Colorado, National Snow and Ice Data Center
Boulder, CO, USA
[email protected]
Mark Meier
University of Colorado, Institute for Arctic and Alpine Research
Boulder, CO, USA
[email protected]
Michael Meredith
British Antarctic Survey
Cambridge, United Kingdom
[email protected]
Kristy Milliken
Rice University
Houston, TX, USA
[email protected]
Carlos Moffat
Woods Hole Oceanographic Institute
Woods Hole, MA, USA
[email protected]
Fen Montaigne
Freelance Writer
Pelham, NY, USA
[email protected]
David Noone
University of Colorado, Department of Atmospheric and Oceanic Sciences
Boulder, CO, USA
[email protected]
Laurence Padman
Earth & Science Research
Corvalis, OR, USA
[email protected]
Mark Parsons
University of Colorado, National Snow and Ice Data Center
Boulder, CO, USA
[email protected]
33
Erin Pettit
University of Washington/Portland State University
Portland, OR, USA
[email protected]
Wolfgang Rack
Alfred Wegener Institute for Polar and Marine Research
Bremerhaven, Germany
[email protected]
Marilyn Raphael
University of California, Los Angeles, Department of Geography
Los Angeles, CA, USA
[email protected]
Ted Scambos
University of Colorado, National Snow and Ice Data Center
Boulder, CO, USA
[email protected]
David Schneider
University of Washington, Department of Earth & Space Sciences
Seattle, WA, USA
[email protected]
Yeong Bae Seong
University of Cincinnati
Cincinnati, OH, USA
[email protected]
Olga Sergienko
University of Chicago
Chicago, IL, USA
[email protected]
Alberto Setzer
Centro de Previsão de Tempo e Estudos Climáticos, Instituto Nacional de
Pesquisas Espaciais
Sao Jose do Campos, Brazil
[email protected]
Andrew Shepherd
University of Edinburgh
Edinburgh, United Kingdom
[email protected]
Christopher Shuman
NASA Goddard Space Flight Center, Cryospheric Sciences Branch
Greenbelt, MD, USA
[email protected]
34
Jefferson Simões
Universidade Federal do Rio Grande do Sul, Laboratoria de Pesquisas
Porto Alegre, Brazil
[email protected]
Susan Solomon
National Oceanic and Atmospheric Administration, Earth System Research
Laboratory
Boulder, CO, USA
[email protected]
Sharon Stammerjohn
Palmer Long-Term Ecological Research, NASA Goddard Institute for Space
Studies & Lamont-Doherty Earth Observatory
New York, NY, USA
[email protected]
Lonnie Thompson
The Ohio State University
Columbus, OH, USA
[email protected]
Manuel Toro
Colorado State University, Center for Hydrographic Studies
Fort Collins, CO, USA
[email protected]
[email protected]
David Vaughan
British Antarctic Survey
Cambridge, UK, USA
[email protected]
Kyu-Cheul Yoo
Korea Polar Research Institute
Incheon, Korea
[email protected]
Ho Il Yoon
Korea Polar Research Institute
Incheon, Korea
[email protected]
Seok-Hoon Yoon
Cheju National University, Faculty of Ocean Science
Jeju, Korea
[email protected]
35
Notes
36